Multi-speed reversible gearing

ABSTRACT

A gearbox for an agricultural tractor comprises forward and reverse gearing connecting an input shaft to a co-axial intermediate shaft, dual-range gearing connecting the intermediate shaft to a layshaft, and 4-speed gearing connecting the layshaft to an output shaft and utilising those of the dualrange gears disposed on the layshaft. The foward and reverse gearing includes a synchromesh clutch, and the 4-speed gearing includes a synchromesh clutch for the highest and the next highest of its speed ratios and a dog clutch for the lowest and the next lowest of its speed ratios. The dual-range gearing includes a cluster of two gears slideable on the intermediate shaft. A power take-off shaft passes through the input and intermediate shafts which are formed as sleeves.

United States Patent 1191 Eastwood MULTI-SPEED REVERSIBLE GEARING ThomasEastwood, Huddersfield, England [73] Assignee: David Brown TractorsLimited,

Meltham, Huddersfield, England [75] Inventor:

22 Filed: Apr. 29, 1974 21 Appl. NO.I 464,952

[30] Foreign Application Priority Data June 3, 1975 PrimaryExaminer-Benjamin W. Wyche Attorney, Agent, or Firm-Norris & Bateman [57] ABSTRACT A gearbox for an agricultural tractor comprises forward andreverse gearing connecting an input shaft to a co-axial intermediateshaft, dual-range gearing connecting the intermediate shaft to alayshaft, and 4- speed gearing connecting the layshaft to an outputshaft and utilising those of the dual-range gears disposed on thelayshaft. The foward and reverse gearing includes a synchromesh clutch,and the 4-speed gearing includes a synchromesh clutch for the highestand the next highest of its speed ratios and a dog clutch for the lowestand the next lowest of its speed ratios. The dual-range gearing includesa cluster of two gears slideable on the intermediate shaft. A powertake-off shaft passes through the input and intermediate shafts whichare formed as sleeves. 1 I

5 Claims, 4 Drawing Figures PATENTEUJm-w SHEET MULTI-SPEED REVERSIBLEGEARING BACKGROUND OF INVENTION This invention relates to gearboxes,particularly but not exclusively for agricultural tractors.

SUMMARY OF INVENTION According to the invention, a gearbox comprisesforward and reverse gearing including a synchromesh clutch andconnecting an input shaft to an intermediate shaft, multi-range gearingconnecting the intermediate shaft to a layshaft, and variable-speedgearing connecting the layshaft to an output shaft.

BRIEF DESCRIPTION OF DRAWINGS A preferred embodiment of the inventionwill now be described, by way of example only, with reference to theaccompanying drawings of which:

FIG. 1 is a front elevation of a gearbox for an agricultural tractor;

FIG. 2 is a section on the line 2-2 in FIG 1;

FIG. 3 is a section on the line 33 in FIG. 1; and

FIG. 4 is a section of a detail on the line 44 in FIG. 2.

DESCRIPTION OF PREFERRED EMBODIMENT Referring now to the drawings, agearbox foran agricultural tractor includes a casing in which there isjournalled an input shaft 11 in the form of a sleeve one end of which isadjacent to one end of an intermediate shaft 12 also formed as a sleeveand journalled inthe casing. The shafts l l and 12 are co-axial,andsurround a long independently rotatable power take-off shaft 13. Agear 14 mounted on splines 15 at said end of the input shaft 11 meshesconstantly with an idler gear 16 rotatably mounted on a needle bearing17 on a dead shaft consisting of a short sleeve 18 secured-to the casingby a bolt 19 and a washer 20. The idler gear 16 meshes constantly with agear 21 formed integrally on a tubular reverse shaft 22 on which anothergear 23 is also formed integrally. The reverse shaft 22 is rotatablymounted on needle bearings 24 on a dead shaft 25 secured in alignedbores 26 in the casing 10 by a detent 27. The other gear 23 on thereverse shaft 22 meshes constantly with a gear 28 rotatably mounted onball bearings 29 adjacent to that end of the intermediate shaft 12 whichis adjacent to the input shaft 11. The gear 28 and the gear 14 each hasformed integrally on it a set of external dog clutch teeth 30 and afemale synchromesh clutch cone 31, and mounted on splines 32 at that endof the intermediate shaft 12 which is adjacent to the input shaft 11,between the gears 14 and 28, there are two hubs 33 separated by acirclip 34 to prevent the transmission of any axial thrust, and eachhaving external clutch teeth 35 like those on said gears. A synchromeshclutch assembly according to our US. Pat. No. 3,695,403 includes aninternally toothed clutch sleeve 36 having a central flange 37 in whichthere are formed an annular groove 38 and three equallycircumferentially spaced chamfered holes 39. A pin 40, having a centralportion of reduced diameter with chamfered ends, passes through each ofthe holes 39, and the three pins 40 rigidly connect together two malesynchromesh clutch cones 41. Two sets of three springs 42, the ends ofwhich abut against three equally circumferentially spaced axialprojections 43 on rings 44, act to centralise the pins 40 axially andlongitudinally of the holes 39. A selector fork (not shown) engaging inthe groove 38 can slide the clutch sleeve 36 along the hubs 33 to eitherside of a neutral position. Initial movement of said sleeve carries thepins 40 and the male clutch cones 41 with it due to the action of thesprings 42, but when one of said cones engages the associated femaleclutch cone 31 the torque exerted by the latter moves the pins 40temporarily off-centre relative to the axis of the holes 39 to preventfurther movement of the clutch sleeve 36 and thus to baulk prematureengagement of the dog clutch teeth until syn chronisation has beeneffected, whereupon the pins 40 are re-centred axially by the springs 42and the clutch sleeve 36 can then slide along the pins 40, afterdepressing one set of the springs 42, to engage its clutch teeth withthe clutch teeth 30 on one or the other of the gears 14 and 28. Thus theintermediate shaft 12 can be driveably connected directly to the gear 14on the input shaft 11 so that both of said shafts rotate at the samespeed and in the same direction, or the intermediate shaft 12 can bedriveably connected to the gear 28 rotatably mounted thereon so thatsaid shaft is driven by way of the idler gear 16 and the gears 21 and 23on the reverse shaft 22 in the opposite direction to the input shaft 11.

Slideably mounted on the splines 32 on the intermediate shaft 12 are twogears 45 and 46 of mutually different-pitch circle diameters securedtogether by a circlip 47 to form a cluster, an O-ring 48 beingcompressed between said gears to damp any tendency for them to moverelative to one another. Formed integrally on a layshaft 49 which isjournalled in the casing 10 parallel to the intermediate shaft 12 arefour gears 50, 51, 52 and 53 the pitch circle diameters of whichdecrease progressively in a direction away from the input shaft 11. Thearrangement is such that the cluster of two gears 45 and 46 on theintermediate shaft 12 is slideable along said shaft by a selector fork(not shown) engaging in an annular groove 54 in said cluster to bringthat gear 45 of said cluster adjacent to the input shaft 11 into meshwith that gear on the layshaft 49 having the largest pitch circlediameter, or alternatively to bring the other gear 46 of said clusterinto mesh with that gear 51 on the layshaft 49 having the second largestpitch circle diameter. Thus the layshaft 49 can be driven in either oftwo different speed ranges relative to the intermediate shaft 12.

An output shaft 55 is journalled in the casing 10 parallel to thelayshaft 49 and has four gears 56, 57, 58 and 59 rotatably mounted on iteach of which meshes constantly with one of the gears 50, 51, 52 and 53on the layshaft 49 to constitute variable-speed gearing. Each of thefour gears 56, 57, 58 and 59 on the output shaft 55 has a set ofexternal dog clutch teeth 60 formed integrally on it and each of thosetwo 56 and 57 of said gears having smaller pitch circle diameters alsohas a female synchromesh clutch cone 61 formed integrally on it. Twohubs 62 separated by a circlip 63 are mounted on splines 64 on theoutput shaft 55 between those two 56 and 57 of the gears thereon havingsmaller pitch circle diameters, each of said hubs having external clutchteeth 65 like those on said two gears, and two similar hubs 66 separatedby a circlip 67 are likewise mounted on the output shaft 55 betweenthose two 58 and 59 of the gears thereon having larger pitch circlediameters. A synchromesh clutch assembly identical to that disposedbetween the gears 14 and 28, and having its parts indicated by the samereference numerals 3644, is slideable on the hubs 62 between the gears56 and '57, by a selector fork (not shown) engaging in the annulargroove 38 in said assembly, to either side of a neutral position forengagement initially with the clutch cone 61 and ultimately with theclutch teeth 60 on either of the gears 56 and 57. A clutch sleeve 68having internal dog clutch teeth 69 is slideable on the hubs 66 betweenthe gears 58 and 59, by a selector fork (not shown) engaging in anannular groove 70 in said sleeve, to either side of a neutral positionfor engagement with the clutch teeth 60 on either of said gears. Thusthe output shaft 55 can be driven by the layshaft 49 at any one of fourdifferent speed ratios. That end of the output shaft 55 remote from theinput shaft 11 has formed integrally on it a bevel pinion 71 adapted tomesh with a bevel wheel (not shown) for driving the rear axle halfshaftsof the tractor via conventional differential gear- The various selectorforks are operable by selector rods actuated in well known manner bygear shift levers.

In operation, any one of the available power paths through the gearboxis selected by appropriate manipulation of the gear shift levers, atotal of eight forward and eight reverse speed ratios being obtainable.The provision of the two synchromesh clutch assemblies facilitateschanging from forward to reverse drive and from the highest to the nexthighest, or vice versa, f the four speed ratios obtainable from thevariablespeed gearing.

I claim:

1. A gearbox comprising forward and reverse gearing including asynchromesh clutch and connecting an input shaft to an intermediateshaft; multi-range gearing connecting the intermediate shaft to alayshaft parallel to the intermediate shaft, said multi-range gearingcomprising a cluster of two gears of mutually different pitch circlediameters slideable on splines on the intermediate shaft so that one ofsaid gears can be brought into mesh with one gear secured on or integralwith the layshaft or alternatively the other of said gears can bebrought into mesh with another gear secured on or integral with thelayshaft; and variable-speed gearing connecting the layshaft to anoutput shaft parallel to the layshaft and comprising a plurality ofgears of mutually different pitch circle diameters secured on orintegral with the layshaft and consisting of or including those gears onsaid shaft forming part of the multirange gearing gears rotatablymounted on the output shaft and each meshing constantly with one of thegears on the layshaft, and clutch means for selectively connecting oneof the gears rotatably mounted on the output shaft driveably to saidshaft.

2. A gearbox according to claim 1, wherein the input and intermediateshafts are co-axial and the forward and reverse gearing comprises a gearsecured on or integral with the input shaft and meshing constantly withan idler gear which meshes constantly with one gear secured on orintegral with a reverse shaft parallel to the input and intermediateshafts, and another gear also secured on or integral with the reverseshaft and meshing constantly with a gear rotatably mounted on theintermediate shaft, and the synchromesh clutch is adapted to connect thegear rotatably mounted on the intermediate shaft driveably to said shaftor to connect driveably together the input and intermediate shafts.

3. A gearbox according to claim 2, wherein the input and intermediateshafts are sleeves surrounding an independently rotatable power take-offshaft.

4. A gearbox according to claim 1 wherein the cluster comprises twoseparately produced gears secured together by a circlip or the like withan O-ring or the like compressed between them.

5. A gearbox according to claim 1 wherein there are four gears on theoutput shaft and the clutch means for selectively connecting one of saidgears driveably to said shaft comprise a synchromesh clutch forselectively connecting either of those two of said gears havingsmaller-pitch circle diameters to said shaft and a dog clutch forselectively connecting either of those two of said gears having largerpitch circle diameters to said shaft.

1. A gearbox comprising forward and reverse gearing including asynchromesh clutch and connecting an input shaft to an intermediateshaft; multi-range gearing connecting the intermediate shaft to alayshaft parallel to the intermediate shaft, said multi-range gearingcomprising a cluster of two gears of mutually different pitch circlediameters slideable on splines on the intermediate shaft so that one ofsaid gears can be brought into mesh with one gear secured on or integralwith the layshaft or alternatively the other of said gears can bebrought into mesh with another gear secured on or integral with thelayshaft; and variable-speed gearing connecting the layshaft to anoutput shaft parallel to the layshaft and comprising a plurality ofgears of mutually different pitch circle diameters secured on orintegral with the layshaft and consisting of or including those gears onsaid shaft forming part of the multirange gearing gears rotatablymounted on the output shaft and each meshing constantly with one of thegears on the layshaft, and clutch means for selectively connecting oneof the gears rotatably mounted on the output shaft driveably to saidshaft.
 1. A gearbox comprising forward and reverse gearing including asynchromesh clutch and connecting an input shaft to an intermediateshaft; multi-range gearing connecting the intermediate shaft to alayshaft parallel to the intermediate shaft, said multi-range gearingcomprising a cluster of two gears of mutually different pitch circlediameters slideable on splines on the intermediate shaft so that one ofsaid gears can be brought into mesh with one gear secured on or integralwith the layshaft or alternatively the other of said gears can bebrought into mesh with another gear secured on or integral with thelayshaft; and variable-speed gearing connecting the layshaft to anoutput shaft parallel to the layshaft and comprising a plurality ofgears of mutually different pitch circle diameters secured on orintegral with the layshaft and consisting of or including those gears onsaid shaft forming part of the multi-range gearing gears rotatablymounted on the output shaft and each meshing constantly with one of thegears on the layshaft, and clutch means for selectively connecting oneof the gears rotatably mounted on the output shaft driveably to saidshaft.
 2. A gearbox according to claim 1, wherein the input andintermediate shafts are co-axial and the forward and reverse gearingcomprises a gear secured on or integral with the input shaft and meshingconstantly with an idler gear which meshes constantly with one gearsecured on or integral with a reverse shaft parallel to the input andintermediate shafts, and another gear also secured on or integral withthe reverse shaft and meshing constantly with a gear rotatably mountedon the intermediate shaft, and the synchromesh clutch is adapted toconnect the gear rotatably mounted on the intermediate shaft driveablyto said shaft or to connect driveably together the input andintermediate shafts.
 3. A gearbox according to claim 2, wherein theinput and intermediate shafts are sleeves surrounding an independentlyrotatable power take-off shaft.
 4. A gearbox according to claim 1wherein the cluster comprises two separately produced gears securedtogether by a circlip or the like with an O-ring or the like compressedbetween them.